Ankara: Turkish rescuers searched for the crew of a cargo ship that sank in a storm in the Black Sea on Tuesday while a second ship was in danger of being overturned by high waves, officials said.

The St Kitts and Nevis-flagged ship, Volgo Balt 199, with 11 Ukrainians and one Russian crew member aboard, was sailing to the Turkish port of Antalya from Russia when it sank off the coast of Istanbul, the state-run Anadolu Agency reported.

The vessel was carrying coal.

The head of the Coastal Safety Directorate, Salih Orakci, told private NTV television that rescue boats and a helicopter were searching for Volgo Balt 199's missing crew, while tug boats had been dispatched to try and help the second ship, the Antigua and Barbuda-flagged BBC Adriatic, further west off the coast of Istanbul.

A television footage showed the second ship with 14 crew members being battered in the stormy waters.

"The sea conditions are very rough which is making the rescue operation very difficult," Orakci said of the BBC Adriatic. "(But) God willing, we will save that ship."

Orakci said the Volgo Balt 199 had not sent any distress signals and disappeared off the radar on Tuesday.